Objective: To answer the question whether the prognosis of women with breast cancer is affected by pregnancy after diagnosis. Material and methods: We used information from the Icelandic Cancer Registry, the Birth Registry and the Genetic Committee. We identified all women who were diagnosed with breast cancer in the years 1927-1992 and who later became pregnant. Controls were women without a history of childbirth after diagnosis of breast cancer. They were matched on tumour size, axillary lymph node status and years of birth and diagnosis, with four year deviation. Results: In the years 1927-1992, 838 women at ages below 50 were diagnosed with breast cancer in Iceland. Of those, 29 gave birth to a child after the diagnosis. Fourteen cases and 33 matched controls fulfilled the inclusion criteria of the study. Survival was better in the group of women who became pregnant after diagnosis, but the difference was not statistically significant (P=0.06). Discussion: Our results do not indicate that the prognosis of women who become pregnant after the diagnosis of breast cancer is worse than of those who do not become pregnant. The group was too small to make definite conclusions. However, the results are in concordance with results from other studies.